1. Field of the Invention
This invention relates to the selective conversion of aliphatic and aromatic dinitriles such as adiponitrile into the corresponding lactam, such as e-caprolactam, by employing a finely divided hydrogenation catalyst, in combination with a finely dispersed co-catalyst. This invention also relates to the selective conversion of a mixture of an aliphatic or aromatic aminonitrile and an aliphatic or aromatic dinitrile into the corresponding lactams by contacting the mixture with a silica catalyst to convert the aminonitrile into the corresponding lactam and thereafter contacting the mixture of lactam and unreacted dinitrile with a hydrogenation catalyst in combination with a cyclization co-catalyst to convert the dinitrile into the corresponding lactam.
2. Prior Art
N-substituted amides, especially 5, 6 and 7 membered lactams, are important raw materials for nylon 4, 5 and 6. Several methods are disclosed in the prior art for preparation of such compounds. For example, U.S. Pat. No. 2,357,484 (E. L. Martin) discloses a vapor phase process for preparing compounds containing the N-substituted amide group, for example, epsilon-caprolactam, by passing a vaporized mixture of water and an aliphatic amino-hydrogen-containing aminonitrile, or a vaporized mixture of water and a nitrile and aminohydrogen-containing amine over a dehydration catalyst such as activated alumina, silica, titanium oxide or borophosphoric acid. U.S. Pat. No. 2,357,484 also discloses that diamides are produced by passing a vaporized mixture of water, dinitriles and monoamines over the dehydration catalyst.